This invention relates generally to an system for use with a distributing assembly, and more particularly to a hydraulic system including functional devices for operating a bulk material distributing assembly.
Conventional discharge assemblies are known to use variable speed drives to control the various functional devices on the bulk material discharge assembly. Known functional devices typically include an airlock discharge assembly, a feed roll, a discharge gate, a floor conveyor and/or an agitator.
The functional devices are known to be powered by hydraulics. In particular, conventional hydraulic assemblies comprise a fixed displacement pump wherein the amount of oil being pumped is directly proportional to the rotational speed of the input shaft. In conventional discharge assemblies, an engine typically drives the fixed displacement hydraulic pump to power the functional devices as well as a rotary lobe type blower to generate the airflow used to discharge the bulk material. In many cases, it is desirable to run at lower engine speeds to decrease the airflow rate. However, running the engine at a lower speed also undesirably decreases the hydraulic fluid flow. In order to maintain the desired performance of the functional devices at low engine speeds, the hydraulic pumps must be oversized, resulting in an undesirable excess capacity when running the engine at full speed.
In the past, priority dividers have been used to divide the hydraulic flow from the fixed displacement pumps into a priority flow and an excess flow. Any flow of hydraulic fluid from the fixed displacement pump is first supplied to the priority side to power the priority devices, and only after the total demand for the priority flow is met will hydraulic fluid be supplied to the excess side for powering the non-priority devices. Thus, as the engine speed is reduced, the blower speed reduces, therefore decreasing the airflow. In addition, decreasing the engine speed also reduces the speed of the fixed displacement hydraulic pump, initially decreasing the speed of the non-priority devices while maintaining the speed of the priority devices at a constant rate. By arranging the feeding devices (e.g., the floor conveyor, the agitator, and the feed roll) as non-priority devices, the engine speed may be used to control the bulk material flow rate. Thus, by reducing the engine speed, the material is discharged with the blower at a slower rate, while the feeding devices also introduce the bulk material into the discharge assembly at a slower rate.
FIG. 1 illustrates a conventional hydraulic assembly 100 having five functional devices comprising an airlock discharge assembly 110, a feed roll 114, a discharge gate 128, a floor conveyor 136, and an agitator 138. The five functional devices are each run by one of two fixed displacement pumps 102, 104. The first fixed displacement pump 102 hydraulically powers the airlock discharge assembly 110 and the feed roll 114. A pressure compensated adjustable priority divider 108 is provided to divide the hydraulic fluid flow into a priority flow and an excess flow. The airlock discharge assembly 110 is a priority device (i.e., the airlock discharge assembly 110 is powered by the priority flow from the first fixed displacement pump 102) while the feed roll 114 is a non-priority device (i.e., the feed roll 114 is powered by the excess flow from the fist fixed displacement pump 102). Accordingly, any reduction in the speed of the first fixed displacement pump 102 will first reduce the speed of the feed roll 114 while the speed of the airlock discharge assembly 110 remains constant. This relationship may be beneficial since the feed roll 114 is one means for controlling the feed rate of the bulk material.
An electric control valve 106 and relief 118 is provided to control the rotational direction of the airlock discharge assembly 110 and feed roll 114. A manual control valve with speed control 112 and relief 116 is also provided to control the speed of the feed roll while allowing the rotational direction of the feed roll to be changed without changing the direction of the airlock discharge assembly 110. Relief valves 116 and 118 are provided to protect against excessive hydraulic pressure. If the system experiences a maximum pressure, the relief valves 116 and 118 will allow additional hydraulic fluid to drain through the exit line for eventual recovery by the hydraulic tank 142. The exit line includes a cooler 120 for lowering the temperature of the hydraulic fluid and a filter 122 for removing impurities from the system before recovery by the hydraulic tank 142.
The second fixed displacement pump 104 hydraulically powers the discharge gate 128, the floor conveyor 136, and the agitator 138. A fixed priority divider 124 divides the hydraulic fluid flow into a priority flow and a non-priority flow such that the discharge gate 128 is a priority device while the floor conveyor 136 and the agitator 138 are non-priority devices. However, since the priority flow of the fixed priority divider 124 is very low when compared to the volume output of the pump 104 at any engine speed, excess flow is always available. The gate circuit on the priority side is protected from over pressurization by the relief valve 130. A manual control valve 126 with relief 130 is provided to control the discharge gate 128, opening or closing the gate 128 depending on the direction the handle is actuated.
A dump valve with relief 140 on the excess side of the priority divider 124 provides a means of actuating the floor conveyor 136 and agitator 138 electrically, and provides pressure protection for this portion of the circuit. An additional adjustable priority divider 132 is provided to give the floor conveyor 136 priority over the agitator 138. Accordingly, any reduction in the speed of the second fixed displacement pump 104 will initially cause the speed of the agitator 138 to decrease prior to any decrease in speed of the conveyor 136. An electrically adjustable priority flow divider 134 allows the floor conveyor 136 speed to be further controlled, with the excess hydraulic fluid being sent to the hydraulic tank 142.
Another conventional hydraulic assembly 200 is illustrated in FIG. 2. The hydraulic assembly 200 has many similar elements as the hydraulic assembly 100 illustrated in FIG. 1, as indicated by the identical reference characters. The hydraulic assembly 200 of FIG. 2 was modified to include three fixed displacement pumps 202, 204, and 205 in an attempt to reduce system vibration.
The first fixed displacement pump 202 was provided to power the airlock discharge assembly 110. A pressure compensated adjustable priority divider 208 is provided to send excess flow through the exit path for later recovery by the hydraulic tank 142. A relief valve 218 was further provided to protect the pump and hydraulic system.
The second fixed displacement pump 204 was provided to power the feed roll 114. A relief valve 216 and another electrically actuated dump valve 217 were provided to protect the second fixed displacement pump 204 and the hydraulic system, and provide means for electric actuation of the feed roll 114.
While functioning advantageously in many applications, these systems are somewhat disadvantageous in that the floor conveyor 136 speed does not slow with a change in engine speed due to being on a priority flow circuit. The relatively low fluid flow requirements of the conveyor 136 will not allow this to be a non-priority function as desired because slowing engine speed would reduce oil flow quickly below an operational level. Moreover, the conventional systems using a fixed displacement pump typically generate excess heat when a great deal of speed control is required. Excess heat is created at pressure drops occurring across the priority dividers. Since the conventional fixed displacement pumps generate flow whether or not in demand by the functional devices, unwanted excess heat is created in the system. It is known to provide a pressure switch 127 to cause an automatic reverse function of the airlock discharge assembly 110. However, these systems do not allow reversing of all functions, for example, to reverse direction in response to objects lodging and/or stalling the functional devices. To do so would add much more componentry, compounding the heat generation of the system.
Accordingly, it is an object of the present invention to obviate problems and shortcomings of conventional hydraulic systems. More particularly, it is an object of the invention to provide hydraulic systems which create a reduced amount of heat during operation, optionally with speed control capabilities. It is a further object of the present invention to provide systems having an autoreverse functional device but prevent inadvertent autoreverse of the functional device in the systems as a result of a pressure spike from a source other than the functional device.
It is another object of the invention to provide hydraulic systems for powering various functional devices at different engine speeds.
To achieve the foregoing and other objects in accordance with the present invention, systems are provided in order to prevent inadvertent autoreverse of at least one of their functional devices. The systems include a variable displacement pump for providing hydraulic power. The systems further include a first device capable of being hydraulically powered by the pump and a reversing device adapted to cause the first device to autoreverse. The systems further include an isolation device adapted to prevent pressure surges resulting from a source other than the first device from actuating the reversing device, thereby preventing undesirable autoreversing of the first device.
To further achieve the foregoing and other objects in accordance with the present invention, hydraulic systems are provided including a variable displacement pump, a first device capable of being hydraulically powered by the pump, and an actuator adapted to actuate a second device based on a pressure surge from the first device. The hydraulic systems further comprise an isolation device adapted to prevent pressure surges resulting from a source other than the first device from actuating the actuator, thereby preventing undesirable actuation of the second device.
Still other objects and advantages of the present invention will become apparent to those skilled in the art from the following description wherein there are shown and described alternative exemplary embodiments of this invention. As will be realized, the invention is capable of other different, obvious aspects and embodiments, all without departing from the invention. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not as restrictive.